Numerous process are known for the preparation of toners, such as, for example, emulsion/aggregation or a conventional process wherein a resin is melt kneaded or extruded with a pigment, micronized and pulverized to provide toner particles.
Rounded toner particles are generally produced via chemical aggregation and coalescence of the toner's various components in aqueous forms. The chemical aggregation process requires all raw materials to be dispersed in water using a surfactant and high-intensity homogenization equipment. Alternatively, chemically produced toners may be produced by solvent-based processes. The chemically produced polyester toners offer the advantage of increased xerographic transfer efficiency due to higher circularity and sharper particle size distribution. However, the chemical aggregation process is water-intensive and time-consuming. Therefore, the chemically made polyester toners are often not competitive against dry toners made by conventional methods.
In a conventional process for producing dry toner particles, the materials are fed in dry form into an extruder and melt-mixed in a continuous, controlled fashion to produce the desired toner characteristics. The materials do not have to be dispersed in water before the extrusion step. Instead, the material from the extruder is physically ground and classified to reach the desired particle size and size distribution. However, an issue that may arise with dry toners produced by the process including extrusion and physical grinding is that the resulting toner particles may be irregularly shaped, rather than spherical. Defects, including toner filming and unstable image quality, can occur where non-spherical toners are used.